Currently, in an electric control system, when a mechanical switch such as a relay controls breaking of load, a breaking electric arc is large, and there is a disadvantage that an electrical life of the mechanical switch is quite short. Therefore, an electronic arc extinguishing apparatus based on a parallel connection between a power device and a mechanical switch emerges, for example, a patent with Chinese Patent Application No. CN01201907.0 and entitled “ELECTRONIC ARC EXTINGUISHER” and a patent with Chinese Patent Application No. CN200910306608.6 and entitled “OPTOCOUPLER-BASED HYBRID AC PASSIVE CONTACTOR SWITCH DRIVING CONTROLLER”. As disclosed in the two patents, a manner of connecting a thyristor (a power device) and a mechanical contactor switch in parallel is used; a control circuit is connected to a control coil of a contactor; before the mechanical contactor switch is broken, a control signal that controls conduction of the thyristor is provided; when the control coil of the contactor encounters a power loss and the mechanical switch is disconnected, the thyristor is turned on, and a filter capacitor of the control circuit discharges to delay disconnecting the control signal for turning on the thyristor; and then the thyristor is turned off, to complete an electric arc-free breaking process.
The foregoing electronic arc extinguishing apparatus has the following disadvantages:
Before the mechanical contactor switch is disconnected, the control circuit needs to provide the control signal that controls conduction of the thyristor in advance.
A driving signal of the thyristor (the power device) is provided by a main loop of the thyristor by using a semiconductor switch, where the semiconductor switch has a high voltage withstand requirement and low reliability, and is prone to breakdown.